GC/C/IRMS Combustion reactor - no peak

[kiki168]

Hello,
I have a problem with our combustion reactor in the lab. Since May he hadn't worked, but in this time it was fine. This week when I run a standart sample I don't see a peaks from the components of the sample. I checked with stream of Ar the connections to the combustion reactor to see if he is broken. Everything is ok. I run a re-oxidation for 2 hours. Also I injected 3 ul air to check for conductivity - again it seems that everything is fine. Then I injected 3 ul breath (5% CO2) - again I have detected a peak. I have changed the septum and inlet with new one. But I still don't see a peak. Could you give me some advices what else I can do and where may be is the problem?

Thank you in advance

[mhr311]

How old is the reactor oven (are you sure of the actual temp) and what is the condition of the Nafion tube?

[kiki168]

The reactor is new - it was installed March this year. The temperature in 940oC. The Nafion tube is of 3 years old. How to check in what condition is the Nafion tube?

[mhr311]

Nafion can tear, pull away from the feed-through connectors or collapse. Also note although Dupont rates Nafion good to about 150C its best to work under 120C. Older Nafion sometimes will get spongy indicating it has been acting as a condenser rather then absorbing and passing out the water vapor. After 3 years its probably best to replace the tubing (OEM usually includes extra tubes in the spares kit), although its a pain replacing it.
You can use something like a hydrocarbon standard (for either C or H) as a test sample. We usually suggest daily standard injection to build known ratios as instrument test.